Hello,

For: Internals>Headless and Platform>DevTools components

The devtools remote debugging protocol does not have any notifications for modification to history state via the window.history apis. I believe that the Page domain would be the ideal place to be notified. 

Filling a bug as per the conversation from this google group post:
https://groups.google.com/a/chromium.org/forum/?utm_source=digest&utm_medium=email#!topic/headless-dev/KRQCJimz730

Thanks, 
Yash Vempati